Electrical switching apparatus



Oct. 13, 1953 w, G OURNE 2,655,568

ELECTRICAL SWITCHING APPARATUS Filed July 2, 1951 Patented Oct. 13, 1953 ELECTRICAL SWITCHING APPARATUS William George Bourne, Acton, London, England, assignor to Rotax Limited, London, England Application July 2, 1951, Serial No. 234,844 In Great Britain July 5, 1950 1 Claim. 1

A known apparatus for starting an internal combustion engine comprises a gas turbin and a carrier for a series of explosive cartridges, which supply the gas required for actuating the turbine. The cartridges are fired successively by electrical means under the control of a switching apparatus.

The primary object of the present invention is to provide an improved switching apparatus for the purpose aforesaid. The invention may, however, b applied to other analogous purposes in which it is required to control a plurality of circuits in sequence.

The invention comprises the combination of a main switch, a selector switch consisting i part of a rotary member for controlling each in turn of a plurality of firing (or other) circuits, a ratchet mechanism for actuating the said rotary member, a main spring for actuating the ratchet and pawl mechanism and for closing the main switch, a manually operable member for energising the main spring, a catch for securing the ratchet and pawl mechanism and releasable by the said member, a catch for securing the main switch in the closed position, and an electromagnet serving to release the latter catch.

In the accompanying drawings:

Figure l is a diagrammatic representation of a switch embodying the invention. Figure 2 is a wiring diagram illustrating the circuits controlled by the switch.

Referring to Figure 1, there is provided a main switch comprising a spring loaded and pivoted arm a which carries a contact 22 co-operating with a stationary contact 0. Also there is provided a selector switch for controlling each in turn of a plurality of firing (or other) circuits. The selector switch comprises a rotary member d having thereon contacts adapted to co-operate successively with contacts e in the firing (or other) circuits to be controlled. Preferably an additional rotary contact member I is provided and adapted to co-operate with contacts g in the said circuits. Where it is required to control three or more circuits two or more of the additional rotary members are provided. The purpose of the additional rotary member is described later.

The rotary member d, f are secured together and to a ratchet wheel 71 which can be rotated in a step-by-step manner by a pawl 2', this being loaded by a spring 7'. Undesired rotation of the ratchet wheel is prevented by a spring-loaded catch it.

The pawl i is pivotally attached at one end to a lever m which is also adapted to actuate the arm a of the main switch, and one end of the lever m is engageable by a tooth n on a catch lever 0 which is loaded by a spring 29.

For actuating the main and selector switches, there is provided a helical main spring :1 mounted on a slidable plunger 7 having a push-button s at its outer end, the spring being supported at one end by the push-button and at the other end by an abutment t. On the other end of the plunger 7 is provided a nose piece it adapted to actuate the catch lever 0. Also the abutment t is provided with an extension 12 which is loaded by a spring w and has thereon a tooth or engageable with a catch lever y which is loaded by a spring a, the catch lever 11 being operable against the spring a by a electromagnet 2 which latter is under the control of any convenient time-delay mechanism.

Th arrangement is such that the first effect of an inward movement of the push button s is to compress the spring q. Further movement causes the nose piece it to actuate the catch lever o and so release the lever m. Also it causes the tooth a: to engage the catch lever y. By the release of the lever m, the spring q is enabled to move the lever m for closing the main switch arm a and imparting an angular movement to the ratchet wheel h. The eiiect of this movement is to cause the contact member d to close a firing (or other) circuit associated with one of the contacts 6. At the same time the member f is moved to short circuit the other circuit through one of the contacts 0. Later the electromagnet 2 comes into action and by releasing the catch lever 11 allows the spring 10 to return the lever m and associated parts to their initial position in readiness for the next actuation of the push button, With the next movement of the push button the main switch is again closed, the contact member d is turned to the position for closing the next firing (or other) circuit, and the contact member I is turned for short-circuiting the other associated circuit.

To enable the operator to effect re-opening of the main switch independently of the electromagnet 2, a push button may be combined with the catch lever y for releasing th tooth x.

Referring now to the wiring diagram shown in Figure 2, this illustrates an arrangement for successively firing two cartridges, and controlled by a switch as above described. The firing circuits are indicated by 3, l and each contains a cartridge 5. The main switch is indicated by b, c, and the push button by s. The releasing electromagnet is indicated by 2 and th associated catch lever by y. The rotatable members which control the firing circuits are indicated by d,

It has been found desirable, in order to minimise risk of inadvertent firing of either circuit, to short-circuit to earth the circuit other than the one containing the cartridge to be fired, and this is ensured by so arranging the contacts on d, 1 that when cl closes the circuit of the cartridge to be fired, connects the other circuit to earth. In series with the firing circuits is preferably provided a resistance 6 for limiting the current which can fiow therein. The closing of the main switch is also accompanied by closing of the circuit through the releasing electromagnet, and a circuit through any convenient time-delay device indicated by l. The said device is adapted to close a switch 8 in the magnet circuit after a predetermined time interval sufficient to ensure firing of the cartridge to be fired. After the one cartridge has been fired the above described operation is repeated causing the member at to close the circuit of the second cartridge, the first being short-cm cuited to earth by the member 1. Where more than two cartridge circuits are provided the member 03 is adapted to close each in turn, and the corresponding additional members I to short circuit the other circuits.

Whilst the invention is primarily intended for use in an engine starting mechanism of the kind specified, it is not restricted to such use, as it may be employed for other analogous purposes in which it is required to control a plurality of circuits in sequence. Also subordinate details of construction may be modified to suit different requirements.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

An electrical switching apparatus comprising in combination a main switch having a movable actuating member, a selector switch having a rotary contact member, a ratchet wheel operatively connected to said rotary contact member. a pawl engaging said ratchet wheel and connected to said actuating member so that movement of the latter in the direction for closing said main switch is accompanied by rotational movement of said ratchet wheel, a catch engageable with said actuating member to prevent movement thereof in the direction for closing said main switch, a manually operable member which upon being moved in one direction encounters said catch and effects disengagement thereof from said actuating member, a spring compressible by said manually operable member during movement of the latter in the direction for encountering said catch, means having a part which forms an abutment for aid spring, and through the medium of which said spring acts on said actuating member for causing the latter to close said main switch upon disengagement of said catch from said actuating member, and a second catch engageable with said means for holding said main switch in its closed condition.

WILLIAM GEORGE BOURNE.

References flited in the file of this patent UNITED STATES PATENTS Number 

